There is an optical scanning apparatus using a multi-beam light source, such as two beams, four beams, and eight beams. The multi-beam light source incorporates, for example, a plurality of laser diodes for emitting beams and one photodiode for detecting light emitted from the laser diodes. In such an optical scanning apparatus, automatic power control (APC) is performed one by one for the plurality of laser diodes. Therefore, the optical scanning apparatus takes longer time for APC as the number of laser diodes provided in the light source increases.